Can an airline really just yank you off its plane?

By now there's a good chance you've seen the shocking video from a United Airlines plane at Chicago's O'Hare Airport. The clip – in which a bloodied man is forcibly dragged off an overbooked flight to make room for an airline employee – has justifiably caused a sensation on social media. And lots of people who saw the fracas must have wondered: Does the airline really have the right to do this?

The short answer, according to aviation and government sources, is that airlines have a lot of leeway to remove a traveller from a plane, for any reason. "Passengers have far fewer 'rights' than they imagine," says George Hobica, president of AirfareWatchdog.com.

It all comes down to the fact that when you purchase an airline ticket, you are technically entering into a contract, known in industry jargon as a "contract of carriage". Few consumers exercise their right to get a copy of the lengthy document, much less read it, but they might reconsider that after this week.

"Airline contracts of carriage do state that your seat isn't guaranteed, and there is language in them to cover refusing to fly someone at their discretion," says Hobica.

Sunday's disturbance all began when United oversold a flight, as all airlines do at times. Other passengers on the flight in question, bound for Louisville, report that after everyone had boarded they were then told the airline needed four people to give up their seats to make room for United employees. (The employees in question were crew members who needed to report for duty the next day, but it's not clear whether passengers knew that fact.)

Anyway, this message reportedly did not sit too well with customers. The situation went further downhill when United was unable to find passengers willing to give up their seats in exchange for compensation.

That's when the "involuntary denied boarding" rules kick in, and if you want to know everything about the sorry-sounding legal term, it's all spelled out in plain English in a government consumer guide called Fly Rights. Basically: When airlines have exhausted all other options, they have to start picking which customers they'll bump, and explain their reasoning in writing. Usually it's based on the fare paid (whoever paid the least gets bumped first), but other factors can be weighed. Airlines do still have to get the unfortunate bumpees to the destination on the next available flight and pay them compensation pegged to the length of the delay.

The issue here that took this situation from bad to worse, and led to the video that's now a deserved PR black eye for United, is the timing. "The burning question is, why did they wait until everyone was seated before realising they needed to move their employees to that flight?" Hobica asks. Most airlines avoid having to yank someone who has already settled in to their seat. Technically, that is still considered a "denied boarding" as long as the plane is still at the gate and is permissible under the law. Just try telling that to the court of public opinion, though, once the world has seen a video like this.

So why can't a passenger simply refuse to leave, as the man in the video did? (He reportedly told the crew he was a doctor and he too needed to be at his destination the following morning for work.) Well, at that point the airline had another legal weapon: Any action or behaviour that is judged to be "interfering with the flight crew" is against the law. "Interfering" is vague and can cover a broad range of passenger behaviour, and can encompass almost anything that makes the flight crew feel uncomfortable.

United, for its part, finally issued a full apology, following news reports that the video had been viewed 1 million times.